High sheen bifilament yarn and elastic textile article therefrom

ABSTRACT

A bifilament yarn comprising two symmetrical lobes fused so that the concave sides intercept at angle theta ranging from 41* to 54*. The yarn has a broad concave area and a narrow edge area of convex shape and preferably a modification ratio of between 1.65 and 2.05. This bifilament yarn, textured and non-textured, semidull and bright, when converted to plain knit hosiery has a luster in the range of 6.6 to 21 (K/S X 100) units. The textured and non-textured plain knit textile articles consisting of the bifilament yarns of this invention after repetitive elongations of 25 percent have 150-300 percent greater work of recovery and equal improvement in resistance to sagging and wrinkling than other cross-sectional configurations. The bifilament yarns are prepared by melt spinning thermoplastic homopolymers having a relative formic acid viscosity of 25 to 60 at a temperature of 250*-280*C through twin orifices separated from each other for a distance of 0.05 to 3.0 mils.

Schuettler et al.

[ 1 Sept. 25, 1973 HIGH SHEEN BIFILAMENT YARN AND ELASTIC TEXTILEARTICLE THEREFROM Inventors: Ralph W. Schuettler, 12800 Percival St.,Chester; Garland L. Turner, Rt. 1, Box 158-A, Chesterfield; George H.Collingwood, 3202 Clay St., Hopewell, all of Va.

Filed: Feb. 18, 1971 Appl. No.: 116,631

Related U.S. Application Data Division of Ser. No. 733,557, May 31,

abandoned.

References Cited I UNlTED STATES PATENTS 3/l967 Opfell 264/174 PrimaryExaminerJohn Petrakes Attorney-Luther A. Marsh 5 7 ABSTRACT A bifilamentyarn comprising two symmetrical lobes fused so that the concave sidesintercept at angle 6 ranging from 41 to 54. The yarn has a broad concavearea and a narrow edge area of convex shape and preferably amodification ratio of between 1.65 and 2.05. This bifilament yarn,textured and non-textured, semidull and bright, when converted to plainknit hosiery has a luster in the range of 6.6 to 21 (K/S X 100) units.The textured and non-textured plain knit textile articles consisting ofthe bifilament yarns of this invention after repetitive elongations of25 percent have 150-300 percent greater work of recovery and equalimprovement in resistance to sagging and wrinkling than othercrosssectional configurations. The bifilament yarns are prepared by meltspinning thermoplastic homopolymers having a relative formic acidviscosity of 25 to 60 at a temperature of 250280C through twin orificesseparated from each other for a distance of 0.05 to 3.0 mils.

7 Claims, 20 Drawing Figures PAIENIEI] SEP25 I975 sun-II 1 or 4 ECT ATTWIST IERY OR SPARKLE E POINT m H 0 FABRIC L4 1.5 I6 L7 L8 L9 2.0 2.I2.2 2.3 2.4 2.5 2.6 MODIFICATION RATIO FIG. 2

I I I SPARKLE I LOOK I l NON.

BIFIL I "I I "6L L SLICK men SHEE -TEXT YAR FALSE T BIFIL YA I R IJ/)I/I 89 x m}: mmhma L5 2.0 2.5 MODIFICATION RATIO FIG. 3

PATENTED SEP2 5 I975 SHEET 2 0F 4 FIG.5

FIGA

FIG.7

FIG.6

PATENTED 2 I973 SHEET 3 OF 4 FIGS FIG.9

FIG.11

FIG.10

FIG.13

FIG.12

em CYCLE FIG. I6

FIG. 19

I LENGTHWISE TFQANSVERSE ELONGATION BICOMPONENT ELONGATION TANsvER'sEGtIh CYCLE FIG. I5

mnouuo lsi mum IO ELONGATION FlG. l8

l BICOMPONEHT ls! CYCLE FALSE TWIST TRANSVERISE FIG. I?

% ELONGATION l0 ELONGATION m. FALSE TWRST This is a division ofapplication Ser. No. 733,557,

filed May 31, 1968, now abandoned.

BACKGROUND OF THE INVENTION Ladies stretch hosiery have usually beenmade from false-twisted round cross section yarn or bicomponent yarnwhere one component is a homopolymer and the other component is acopolymer arranged either side by side with the homopolymer or as a corein a sheath and core arrangement. Such yarns, while finding utility inladies hosiery, have a disadvantage in that three or more sizes arerequired to cover the range of sizes 8-% to l l-Vz. This range of sizesamounts to about 99 percent of the ladies hosiery consumption in theUnited States. Additionally, various cross-sectional types such astrifilament, triangular, Y-cross section, star cross section, polygonal,and the like, have been employed to achieve decorative effects in thesehosiery. When these conventional yarns are employed, three or more sizesare required to cover the practical range of hosiery sizes, andgenerally, the modified hosiery has either too dull an appearance or toomuch glitter with the latter having utility only for its novelty effect.

There has long been a need for a true stretch hosiery where one sizewill fill the majority of end-use requirements and which has sufficientluster and sheen to be desirable for formal wear without being toogarish for everyday and business use. It is also highly desirable toproduce a true stretch yarn having adequate power of recovery tomaintain a good fit without wrinkling or becoming permanently deformedunder severe bending action, such as deepaknee bends. Additionally,hosiery yarns made from too components, a homopolymer and a copolymer,are expensive and difficult to produce. Thus, there has long been a needto produce a stretch yarn which avoids the described problems, and moreparticularly, it has been desirable to produce said yarn from a singlehomopolymer.

In an attempt to simulate some of the geometric forms of natural fibers,various configurations including bifilament yarns were produced almostfour decades ago from man-made cellulosic fibers as disclosed in SwissPat. No. 145,408 dated Feb. 28, 1931. Since this time, several patentshave issued showing various configurations representing a range of fibertypes which have two or more lobes. For example, US. Pat. Nos. 3,156,607and 3,131,427 illustrate yarn configuration which are essentiallybilobal. Thus, the prior art is replete with patents showing varioustypes of bilobal yarns yet none of the patentees recognized the criticalnature of the angle of intercept between the two lobes which isessential in producing a high sheen hosiery yarn that does not have agarishness related to excessive sparkle. I

Additionally, when such multilobed forms are used in ladies hosieryirrespective of the texturing method employed, three or more sizes ofstretch hosiery are required to cover the range of consumer sizes.lndeed, to have truly satisfactory fits in stretch hosiery, five sizesare judged by independent laboratories as being necessary to suit mostconsumer requirements for a comfortable as being necessary to suit mostconsumer require-v ment for a comfortable and attractive fit.

There has been still another problem with prior art yarns in that thestretch qualities on repeated stretching of hosiery results in continuedloss of the original stress-strain properties and sagging or wrinklingof the hosiery may occur, particularly at the ankle section and kneesection. With the foregoing discussion in mind, the provision for ahomopolymer yarn which possesses the desired appearance factors as wellas the desired stretch properties represents a substantial improvementin the art.

SUMMARY OF THE INVENTION The product of this invention involves athermoplastic homopolymer fused into an oblong shape having twosymmetrical lobes fused so that the concave sides intercept at an angle0 ranging from 41 to 54, preferably 4252. The bifilament yarn has abroad concave area and a narrow edge (convex) area so that when saidyarn is placed in a knit structure, the broad concave areas becomealigned facing each other at stitch crossing points to present a convexor edge area to view and twist or more to present the concave or broadareas to view in the loop sections. Light reflects from each concavearea presented to view in the loop areas as a minute point flash and thealignment of these minute point flashes result in a sheen or opalescencewhich is enhanced in bright yarns and reduced if a delusterant ispresent. Because of its geometrical configuration false-twist bifilamentyarn has twice the number of twists trapped in each loop and twice thenumber of point flashes; therefore, an enhanced luster or sheen isobtained in plain-knit hosiery.

Likewise, this twist trapped in each loop of the knitted structure givesgreatly increased multidirectional elastic properties to the gridstructure since each twist in each loop, coarse and wale becomes amultiple of the total number of loops of the grid structure therebygreatly enhancing its elasticity.

The preferred modification ratio is 1.65 to 2.05 and more preferably1.75 to 1.95 and the tip radius is generally 0.9 or greater. Thebifilament yarns, textured and non-textured, semidull and bright, whenconverted to plain knit hosiery as an undyed boardered structure haveluster values as follows:

Bright Non-Textured Bright False-Twist These high luster values are dueto alignment of minute point flashes resulting in a high glossy sheentermed the glace look or wet look for bright yarns. This high sheen anduniform luster has not thus far been obtained in prior art knittedstructures.

The preferred process for producing the yarn as above described involvesemploying a polyamide having a relative formic acid viscosity of between25 and 65 which is extruded through a pair of spinnerette orificeshaving a distance between said orifices of 0.5 to 3.0 mils, preferably1.0 to 2.5 mils. Nylon 6 is spun at a temperature of between 250 and280C, preferably 265 to 275C, and nylon 6,6 is spun at approximately 10higher temperature. The polyamide relative formic acid and the distancebetween the spinnerette orifices are the two major variables asindicated hereinafter in Table 1. With an increase in relative formicacid viscosity, the modification ratio increases and the angle ofintercept decreases and the luster values increase. Thus, a sparkle lookis produced and the desired high sheen glace look" is lost. It is noted,also, that the temperature of the polymer melt must be considered. Astemperature increases, the modification ratio decreases. Additionally,at too high a temperature, drips, breaks and wraps may appear, which areundesirable in the processing of such fibers.

Thermoplastics in general can be employed for producing bifilamentyarns, but because of their excellent dyeing properties and good opticalproperties, polyamides usually are preferred for the production ofbifilaments in accordance with this invention. Preferred polyamides arepoly-e-caprolactam (nylon 6), polyhexamethylene adipamide (nylon 6,6),and the polyamides made by condensation ofp,p'bis(paraaminocyclohexyl)methane with dodecanedioic acid to producethe polyamide poly[bis(paminocyclohexyl)methane dodecamide].

The bifilament yarns disclosed as the invention herein have utility intransport upholstery and apparel end uses because of the high elasticityof the knitted structure and the high glossy sheen or glace look whichcharacterizes knitted textile articles made from bright bifilaments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section of thespinnerette orifices employed to extrude the bifilament yarns of thepresent invention.

FIG. 1A is a cross-sectional view representing the bifilament yarn ofthis invention illustrating how the angle of intercept 6 is measured.

FIG. 2 illustrates graphically the relationship between the opticalproperties of the filaments as a function of the angle of the bifilamentintercept point versus the modification ratio.

FIG. 3 is a graph illustrating the luster of bifilament yarns of thisinvention plotted against the modification ratio. These data illustratethe change in sheen between false-twist and normal yarn. The dottedlines show the range of modification ratio which produces the preferredhigh sheen yarn.

FIG. 4 is a photograph illustrating, at 320 magnifications,representative cross sections of undrawn bifilament yarns of the presentinvention which have a modification ratio of 1.7.

FIG. 5 is another photograph at 320 magnifications of other bifilamentundrawn cross sections which have a high sheen glace look when the yarnis placed in a sheer fabric. Generally, above this modification ratio of2.0, a transition to the sparkle look occurs.

FIG. 6 is a photograph at 560 magnification of a typical cross sectionof drawn bifilament yarns having a modification ratio of 2.3 to 2.4.

FIG. 7 is a photograph at 900 magnifications of a drawn bifilament yarnhaving a modification ratio of 2.8 to 2.9.

The yarns of FIGS. 6 and 7 are outside the critical range required toobtain a glace look".

FIG. 8 is a photograph illustrating the unique property obtained bycombination of bifilament geometry with a false-twist operation. Thisillustrates the alignment of the concave surfaces at stitch cross-overpoints and the twist which in the loop part exposes the broad parts ofthe concave surface to view. This additionally illustrates the alignedrows of point light reflections from concave surfaces to give the uniquesheen which can be observe. The magnification of FIGS. 8 through 13 is36X.

FIG. 9 is a bifilament yarn in jersey knit hosiery which was notfalse-twisted. There is similar twist entrapment and alignment of thelight reflective areas as in FIG. 8.

FIG. 10 is a photograph of a round cross-sectional yarn which isfalse-twisted and knit into hosiery. It can be observed that the lightreflective areas are completely random, there is no twist between thestitches, and the yarn tends to curl back on itself rather than betwisted between the stitches.

FIG. 11 is a photograph of round monofilaments of plain knit hosiery. Italso lacks the properties of twist entrapment and luster effectscharacteristic of bifilament yarns as illustrated in FIG. 9.

FIG. 12 is a photograph of stretch hosiery of round cross section,bi-component filaments. Again, there is no alignment of the light areasin the yarn. Consequently, there is no luster or sheen, or enhancementof the elasticity from twist trapped between stitches.

FIG. 13 is a photograph of mesh hosiery tuck stitch made from trilobalor triangular shaped yarns. As can be observed, the light reflectionareas are random and significantly larger than those illustrated inFIGS. 8 and 9. Such yarns while suitable for many novelty end-uses haveutility only as novelty yarns because of the garishness of the luster.

FIG. 14 is a graph illustrating the force required to elongate abi-component stretch yarn after one cycle of elongation, and, after sixcycles of elongation. The stretch direction was lengthwise and the testsample was ladies hosiery with plain knit construction.

FIGS. 15 and 16 represent the same test parameters as for FIG. 14 exceptthat FIG. 15 represents false-twist bifilament yarns of this inventionwhich have superior elastic properties over that for FIG. 14 and FIG.16. FIG. 16 represents false-twist round cross section nylon 6 yarn.

FIGS. l7, l8 and 19 represent, respectively, leg sections of ladieshosiery made from false-twist bifilament yarn, false-twist roundfilament yarns and round cross section bicomponent sheath and core yarn.The nature of the test data illustrated in these figures is similar tothat described for FIGS. 14, 15 and 16, except the measurement is in thetransverse direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The bifilament yarns of thepresent invention preferably are spun from a polyamide such as nylon 6or nylon 6,6 directly from a continuous polymerization system whereinthe polymers are melted prior to extrusion using an extruder or amelter. The molten polymer is then extruded through a pair of orificesin close proximity to each other as depicted in FIG. 1 by capillaries land 3. These capillaries are separated by the portion 2 which ispreferably an integrate portion of the spinnerette plate 6. The moltenpolyamide polymer enters through an entry orifice denoted at 5 and isdivided into separate streams on contacting metallic portion 2. Thedistance between orifices 1 and 3 should be between 0.5 to 3.0 mils. Thedistance when less than 0.5 mils results in the separator portion 2, tooweak to withstand the extrusion pressure. Should the distance betweenorifices 1 and 3 exceed 3.0 mils, one then enters the region of asparkle effect and the preferred glace look is not obtained. The lengthof spinnerette orifice 4 should generally be in the region of 0.8 to 4times the diameter of the spinnerette orifices l to 3, preferably alength to diameter ratio of about 1.2 should be employed.

The yarn product of the present invention has a glace look which hasbeen described as a wet look when fashioned into articles such as ladieshosiery and other sheer garments. This appearance is achieved only whencritical parameters are observed during the production of the bifilamentyarns of this invention. It is essential that the yarns intercept at anangle of between 41 and 54 of the joined filaments. It is also preferredthat the yarns have a modification ratio ranging from 1.65 to 2.05. Atan intercept angle of greater than 54, too low a luster is obtained andtwist is not trapped between the filament loops to achieve the desirableelasticity properties in knit structures. At an angle of intercept below41, the yarn exhibits a sparkle effect and does not have the glace lookand desirable opalescent sheen of the product made in accordance withthis invention.

The angle of intercept is determined by completing the two circlesoutlined by the filament lobes 12 and 14, then completing a linebisecting the center of the circles and the point where the circlesintercept as shown in FIG. 1A. The angle of intercept is the angle 6between the horizontal line passing through the center and the linedrawn to the intercept point.

The modification ratio is determined by dividing the minimum width atthe point of upper and lower intercept points of the two circles intothe length or the distance to the outer perimeter of the two circles.The relationship between the angle and the modification ratio isgiven'in FIG. 2 wherein it is illustrated that as the modification ratiodecreases, the higher the angle of intercept. I

As can be observed in FIG. 2, the glace appearance coincides at an angleof intercept between approximately 38 and 56, the area represented byABCD.'At a lower angle of intercept, the glace look is lost and asparkle effect occurs. At a broader angle of intercept than 54, ther isinsufficient luster and the bifilaments lose most of their ability toalign face to face at stitch cross-over points, the condition whichimparts twist to said bifilaments in the loops between stitches.Therefore, they lose their luster, but most important, they lose theirelasticity because of inability to trap twist between each stitch in theknitted structure. It is especially desirable that an angle of interceptbe present on both sides of the bifilament yarns so that the twist isalways trapped between stitches regardless of which side of the concavesurfaces align at the stitch crossing points.

In FIG. 3 is shown a plot of the modification ratio versus luster.Luster is ascertained by measuring light reflectivity with a Color Eyemanufactured by the Instrument Development Laboratories, Attleboro,Massachusetts. The reflectivity is expressed by the Kubelka Munkequation where:

(K/S) ([1 R] /2R) where R reflectivity ascertained with the C6161 Eye"at 557 millimicrons. The method for ascertaining the reflectance hasbeen described in Color and Business, Science and Industry by D. B..ludd: John Wiley and Sons, New York, New York, 3rd printing, February1967, pp. 434-438. As can be observed in FIG. 3, the luster values ofsignificance are from 9 to 21 (K/S X units, preferably 10 to 18 (K/S X100) units. For false-twist bifilament yarns, the luster values arequite significantly higher than non-textured bifilament yarn made intohosiery. This is due to the presence of approximately twice as manyconcave reflection points in each stitch loop of textured over thenon-textured bifilament yarn. Hosiery fashioned from the texturedbifilament yarn have luster values of 14 to 21 (K/S X 100) units. Thepresence of this additional reflective surface or additional number ofreflection points results in a considerable enhancement of the desirableglace look over that obtained from the same hosiery made fromnon-textured bifilament yarns. This enhancement of the glace look by apanel jury evaluatiori of skilled colourist's amounts to 200 to 300percent increase in the apparent sheen or luster values observed.Non-textured bifilament yarn has a luster value of8 to 16 (K/S X 100)units. At lower values than the indicated range of bright luster,insufficient luster is present to produce a sheen effect. At higherluster values, as, for example, greater than 16 for the nontextured andgreater than 21 for the false-twist hosiery, there is excessive sparklein the hosiery which tends to limit their utility to novelty end uses.

Generally, within the scope of the luster values indicated, and as shownin FIG. 3, this hosiery is quite acceptable to be worn in everydayoffice use and still quite attractive and desirable for formal wear. Theluster values for semi-dull yarns having the same modification ratio asbright yarns are quite different and only a low level'of surfacereflectivity is obtained. The major effect is a significant increase incover due to the visual appearance of the broad concave surface in theloop section of the knitted structure. The increase in cover is 10-20percent greater than round cross section yarn ofthe same denier.

A better appreciation for the critical influence that the angle ofintercept and modification ratio of the yarn has upon appearance and theperformance of the yarn of this product of this invention can berecognized from an investigation of FIG. 4 through FIG. 19. FIGS. 4 to 7are photomicrographs of cross sections of bifilaments illustratingproducts of the invention compared with bifilament cross sections thatare outside of the invention. The modification ratio of the crosssections shown in FIG. 4 is 1.7 and as can be observed there is only aslight distinct concave surface. Thus, the bifilaments having valuesbelow 1.5 and are not concave and generally have neither luster nor theelasticity desired. FIG. 5 is a cross section having a modificationratio of 2.0 which represents the upper limit beyond which excessivesparkle occurs. FIGS. 6 and 7 have modification ratios substantiallygreater than 2.0 and thereby representing yarns outside the scope ofthis invention.

FIGS. 4 and 5 illustrate the cross section of undrawn yarns and FIGS. 6and 7 illustrate a cross section of drawn yarn. As can be observed,undrawn and drawn cross sections at equivalent magnification haveidentical geometric cross sections.

Again, when referring to FIG. 1A and FIGS. 4 through 7, it can be notedthat when the circles are completed, as indicated in FIGJJA for circles12 and 14, the total area of this circle is determined and theirmeasured perimeter is divided into the perfect circle enclosing themeasured area. From this arrangement their degree of circularity can beascertained. Preferably the yarns of this invention have a degree ofcircularity of greater than 0.9. Bifilaments having a substantiallylarger deviation from circularity do not have the same sheen andknitting is difficult because of the tendency of such yarns to break outfrom back-up of twist at the needles.

The performance of hosiery fashioned from bifilament yarns made inaccordance with this invention is compared with hosiery made from otheryarns in FIGS. 8 through 19. These comparisons are made on the knittedstructures since the unusual properties of light reflectivity andelasticity can be observed, and measured only after the yarn is placedin a fabric construction. It should be emphasized that hosiery are usedas a common example; however, bifilament yarns react in a similar mannerin otherjersey knit structures as well as, tricot knit structures, meshor tuck stitch structures, and rib stitch structures.

FIG. 8 illustrates a section of hosiery fashioned from bifilament yarnshaving a modification ratio of 1.8. The yarn has 31 turns per inch oftwist imparted thereto, utilizing a Leesona 553 Superloft machine. It isknitted into the hosiery using S and Z twist in alternate courses. Itcan be observed from FIG. 8 the light areas are short in length due tothe twist of bifilament yarns between stitches; however, as can benoted, the light areas are all on an approximate similar plane. Thisresults in a diaphanous, luminous sheen, which has been characterized asthe glace look." As the modification ratio of bifilament yarns isincreased, the length of the light flashes increases. As the intensityof the light at these points increases, each individual light-coloredpoint results in a scintillation point, and the luminous sheen effect isreplaced by a sparkle effect. Between each stitch it can be noted thatthe bifilament yarns twist 90 degrees first to present a flat plane toview and over the course of the twist, at least another 90 degrees for atotal of at least 180 degrees to present two concave planes to view. Itis this twist superimposed upon the false-twist stretch that lendssufficient elasticity to the hosiery so one size will span the range ofsizes for most consumer end uses.

Additionally, as the stitches in FIG. 8 are stretched, the twist that istrapped between the stitches in the manner stated above graduallyuntwist and when tension is released, these twists rewind. Afterstretching, particularly in areas of hosiery where elongations ensue,that is, the areas which have greater propensity to sag or wrinkle, thetwist which has been unwound as the individual stitches are stretchedout, rewind into a normal configuration and provides additional forcesuperimposed on that from the false-twist crimp. Thus, the combinedforces, at low elongation, are adequate to hold the hosiery firm to theankle or firm to the knee without any evidence of sagging or wrinkling.Moreover, such hosiery resists elongation on repetitive cycling. I

In FIG. 9, a bifilament yarn the same as in FIG. 8, except withoutfalse-twist, illustrates that all light reflection areas are located atrelatively precise points in the center of the plain-knit stitch andalong the sides of the stitch. Thus, the bifils present the interceptpoint on a flat plane in the direction of the light and in the directionof the observer's view. In a comparison between the false-twisted andnon-false-twisted yarns, it can be observed that the light areas andstitches are more uniform for the non-twisted yarn, and that the lightareas are in a precisely aligned plane. It is this alignment of thereflection areas, which results in the smooth luminous sheen. This rnaybe compared with round cross section yarn in FIG. 11 which exerts notwist entrapment and has essentially no light reflective areas.Additionally, it may be compared with a trifilament yarn cross sectionin a mesh knit as illustrated in FIG. 13, where the point flashes extendover the long length of the tuck stitches and over broad areas of thestandard jersey knit stitches. These broad areas of light reflectionpromote too much sparkle for most end uses, particularly for office wearand additionally as can be noted, there is less or no twist entrapmentbetween stitches in FIG. 13.

FIG. 12 illustrates a time exposure for round cross section bicomponentelastic yarns. As can be observed, only small sparkle areas areobtained, and if it were not for the lengthy time of exposure, thissparkle could not be observed. Additionally, as can be observed, thereis no twist entrapment between the stitches.

In FIG. 13 it can be observed that there is a bright sparkle in thecenter stitch. It is these large point sparkles that follows the entirelength of the stitch which would seen to indicate there is relativelylow level of change in planes of the reflecting surface. Therefore, nosignificant improvement in elastic properties or sheen could be expectedfrom the yarn as illustrated in FIG. 13. Additionally, the sparkle istoo bright except for formal occasions.

FIG. 14 illustrates the stress-strain characteristics of a plain knithose manufactured from a commercial bicomponent round fiber after onecycle and after six cycles. As can be observed, there is almost completeloss of stretch power after six cycles, particularly at 3 percentelongation. Moreover, the values at 5 percent elongation are quite low.However, after these initial elongations there is a rapid increase inthe gram loading for small increases in the elongation. It is this rapidincrease which is undesirable because there is too much of a load for agiven degree of stretch. This type of loading causes an uncomfortableeffect on the part of the wearer as well as impart stresses to theindividual filaments so that a sudden pick on impact will probablyresult in a run in the hosiery or garment.

FIG. 15 illustrates the lengthwise extension versus stress-strain loadfor a hose constructed the same as in FIG. 14 except the bifilament yarnof this invention which has been false-twisted was employed. As can benoted, the hose has a definite initial loading that is still higherafter six cycles of extension which slopes upward at a substantiallylower rate than that described in FIG. 14. Thus, it has a relativelyuniform stretch characteristic maintaining a definite power afterrepetitive stretching sufficient to avoid wrinkling or sagging of thehosiery.

FIG. 16 represents hosiery processes in identical manner to thatillustrated in FIG. 15 with the only difference being round crosssection versus bifilament yarns. Again at 3 percent elongation, aftersix cycles, there is no power left in the yarn and sagging or wrinklingcan occur. Additionally, there is considerable greater drop in the loadat 5 percent elongation from the first to the sixth cycle. Generallythere is a slower increase in loading with a substantial increase inelongation for the round false-twist yarn than that for the bifilamentyarn, as illustrated in FIG. 15, when tested in a lengthwise direction.

False-twist triangular or trilobal cross section yarn is converted intohosiery and processed in identical manner to that as illustrated in FIG.with the only difference being round cross section bifilament yarnversus the round cross section of FIG. 16. Again this cross sectionexhibits very low load capacities after six cycles which is similar tothat for round cross section falsetwist yarn, except that at 10 percentelongation and above, loading is very rapid, even more rapid than thatillustrated in FIG. 15. This would cause an uncomfortable effect on thepart of the wearer as well as stress individual filaments to increasethe potential of runs or breakage of the filament from sudden picks orimpact.

FIG. 17 illustrates a bifilament yarn in the transverse direction.Comparing FIG. 17 with FIG. 15, it can be observed generally there is afar lower increase in loading in the transverse direction for a givendegree of elongation than there is in the lengthwise direction. It is,however, an unexpected advantage of the bifilament yarn, that it has adefinite and significant loading capacity even at elongations as low as3 percent which still remain adequate after six cycles of extension.

FIG. 18 shows exactly the same transverse stressstrain curve for afalse-twisted round cross section yarn. As can be noted at lowelongation, 3 to 5 percent after six cycles, the false-twist yarn hasessentially no load-bearing capacity. Therefore, it would tend towrinkle. In a similar manner, a triangular cross section false-twistedyarn shows essentially the same initial transverse stress-strain curveas that for round cross section, and then very rapidly loads which is anindication of limited and narrow elastic characteristics.

FIG. 19 illustrates a bicomponent yarn in a transverse extension. Thisyarn also has very low-bearing capacities throughout the range tested upto 25 percent elongation. Again, if wrinkling should occur, it moreprobably would occur with the bicomponent yarn of FIG. 19 than with theyarn of FIG. 18, and especially with yarn of this invention illustratedin FIG. 17.

From the foregoing illustrations and comparisons made in connection withthe drawings, it can be seen that, in general, the luster of bifilamentyarns is a function of the modification ratio whether a glace look" or asparkle effect is obtained. Other configurations show quite differentluster effectsand do not normally demonstrate the silky high sheencharacteristic of the modification ratio of between 1.65 and 2.0, whichis illustrated in FIGS. 2 and 3. Many end-uses of knit apparelstructures require a low degree of transparencey. To achieve thiseffect, anatase titanium dioxide is dispersed in the monomer or at somepoint prior to completion of the polymerization cycle in the amount of0.3 percent of Ti0 by weight of polymer for semidull articles and 2.0percent by weight of Ti0 by weight of polymer for full-dull articles.This delustering quality is desirable for its hiding power, butfrequently it has undesirable chalkiness or grayishness which decreasesthe aesthetic properties of the textile article containing saiddelustrant. Thus, when the bifilament yarn of this invention is madeinto knit textile articles, an enhanced warmth of appearance andaesthetic properties is obtained. The delustered yarn has 10-20 percentgreater cover on a standard hosiery form as compared with round crosssections of equivalent denier. The high luster obtained for bright yarnhas the further advantage in that the high degree of reflectivity whichis obtained significantly reduces the apparent soiling as compared withround cross sections and triangular cross sections.

The following examples furthe illustrate the invention.

EXAMPLES 1 14 The bifilamentary yarns of the present invention wereprepared from polycaproamide pellets of 50 to relative formic acidviscosity which were spun at a temperature of 255 to 260C from a melterthrough twin spinnerette orifices, 10 mils in diameter by 10 mils inlength and separated from each other at a minimum distance of 2 mils.The spinnerette employed had a counterbore angle of as indicated byreference numeral 5 in FIG. 1. The molten polymcrentercd the spinnerettecounterbore at the rate of 4.78 grams/- minute/bifil filament. Therewere four spinnerettes per stack, each spinnerette producing two strandsof bifilament yarn and each spinnerette was separately metered. Thus,eight strands of bifilament yarn were produced per quench stacloThe yarnwas quenched 3 inches below the spinnerette face with quench airentering at the temperature of 41C and traveled uniformly transverse tothe filaments, at the rate of 10 lineal feet/min. for a distance ofinches from the point of initial gas contact with the filaments. Theyarn then entered a round quench stack of about 7 inches in diameter,thence over a lubrication roll where finish was applied at about 8 to 10percent by weight of yarn. The yarnvwas then taken up on a winder havingtwo cops per sleeve and using four sleeves per winder making a totalnumber of eight ends per winder having 4.7 pounds/cop or 9.4pounds/sleeve. The speed of takeup was 1,950 feet/min. for the undrawnyarn. The bifilament yarn was then placed on drawtwisters passed 1.5wraps around an Armstrong Rubber Compound 732 cot roll, thence 4 wrapsaround a draw roll, thence to a cylindrical core where a filling wind orpineapple wind was employed for hosiery. A warp wind was employed fortricot and other sheer-type fabric. The rubber cot roll employed had ashore hardness of 50. A higher value resulted in difficulty inmaintaining the bifilament under the cot roll.

The draw ratio between the cot roll and the draw roll was 3.98 and thedrawing speed was 3,050 feet/min. The yarn contained about 0.2turns/inch twist and the drawn denier was 20. The weight of the yarn onthe pirns was approximately 2 pounds. The yarn was then placed on aLeesona 553 Superloft false-twisting machine and false-twisted to atwist level of 31 turns/inch, at a heater temperature of 182C and aspindle speed of 198,000 rpm. The yarn was fed into the twisting zone ata speed 6 percent slower than it was discharged from the twisting zone.The final package weighed 1 pound.

Round cross section polycaproamide yarn was prepared in a conventionalmanner, false-twisted with the same number of turns per inch as that forthe bifilament yarns for use as a control yarn. These yarns were knittedwith a Textile Machine Works Mark IV 400-needle, 4 feed ladies circularknit hosiery machine, into hosiery 35 inches in length which contained2,100 courses throughout the full length of the hosiery, for an averageof 60 courses per inch. The boarded hosiery contained at the ankle 74wales per inch and 48 courses per inch. At the welt the hosierycontained 60 wales per inch and 66 courses per inch after boarding.

The poiycaproamide yarns were boarded at a temperature of 118C forbifilament yarns and 108C for round cross section yarns, bothtemperatures being the maximum suitable for the particular cross sectiondescribed in order to obtain the best stretch properties.

The bifilament yarns of this invention were knitted utilizing a tuckstitch on a Fidelity 2-feed circular knit machine for production ofladies mesh knit hosiery for a comparison with hosiery of the sameconstruction utilizing filaments having a triangular cross section.

After preboarding, the luster properties of these hosiery weredetermined as well as some special bifilament yarns prepared underconditions to produce different cross-sectional modifications which aredescribed in example 17. The method for obtaining luster values listedin Table 1 is given in the description herein. The interpretations as toquality of the appearance are based on the dyed hosiery placed over astandard leg form and the values are recorded as the average ofobservations from a panel jury of experienced coiourists. Observationswere made under fluorescent light and in bright daylight. Brightdaylight assisted in showing the demarcation between sparkle and theglace look of the hosiery. It was noticed by the panel jury of judges,that daylight emphasized sparkle, but subdued internal lightingemphasized the glace look. The ratings of the panel are listed in Table1.

The true visual rating for the increase in sheen for the false-twistbifilament yarns as compared with the nontextured bifilament yarns was200 to 300 percent cant value since it means that the bifilament yarnshave an improvement in sheerness values of I percent without a loss inwearing properties as would normally be expected with a correspondingreduction in the denier typically required in round cross sectionhosiery to achieve the present sheerness values.

The improvement in sheerness is due to alignment of the concave surfacesfacing each other at stitch crossing points so as to present the narrowedge to view.

All luster values listed in Table l were ascertained using a color eyefabric sample holder with a black background and employing a Model D-lColor-Eye.

The boarded stockings were dyed in a conventional manner, dried by thetray method and placed in an Instron tester to evaluate the stretchproperties of the hosiery. The hosiery were pretensioned at 1 percent ofthe total lnstron loading which was 500 grams minimum and 2,000 gramsmaximum. Thus, the pretensioning was between 5 and 20 grams, dependingupon the degree of stretch in the hosiery being tested and the loadsrequired to elongate the hosiery to 25 percent.

The lnstron was equipped with G61-3C air-operated clamps gripping for adistance of 2 inches and the two jaws were separated from each other bya distance of ute on. the loading part of the cycle and at the same rateon the unloading part of the cycle.

TABLE 1.OPTICAL OR LUSIER PROPERTIES AS MEASURED ON THE BOARDED IIOSIERYPercent Modifi- Angle of luster K/S Type cross cation blfilarnent by"color Example number section ratio intercept eye" Panel jury rating ofthe degree of silky sheen glue look" Bifilament 1. 4 62 6.0 No sheen,similar to round. do l 1.65 55 10.0 Good (A) subdued sheen. d0. 1. 62. 510-20% greater cover over Example 6A. d0 1.8 49.2 12.0 Excellent strongglace look high sheen. do- 1.95 44 1020% greater cover compared withExample 6A. d0. 2.0 42.5" 14.0 Good (B) glac look with slight sparkle.do 25 27 24.0 No glae look," definite sparkle.

Round- 1. 0 4.6 No "glac look. .do 1.0 Dull without warmth.

Triangular 45. 0 Heavy sparkle, too garish for most end-uses in hosiery.F-T triangular Heavy sparkle. F-T bifilament.". 1.7 525 15.5 Good (A)subdued glac look.

1.8 49.2 Subdued sheen. 1.9 46 18.0 Excellent strong glac look." do 2.0541 12. 0 subdued warm sheen.

F-T round 1. 0 3. 6 No glac k. F-T bifilament.--- 2. 5 42 23.0 No "glac100k," definite sparkle.

'F'I=false twist. Luster is measured on the white boarded hosiery beforedyeing. The panel jury 015 experienced coluorists rating is based onobservatlon oi the dyed hosiery, and is as follows:

Exceent=0palescent smooth silky high sheen, the preferred glac GoogdM);Opalescent silky sheen glac look present but slightly su ue Good (B)=Anopaleseent high sheen with the preferred glae look" but some sparklepresent. Br=bright hosiery. (Delustrant) SD=Semidull=0.3% by weightanatase TiOz.

TABLE 2.FORCE IN GRAMS FOR HOSIERY EXTENDED LENGTHWISE AT THE INDICATEDELONGAIIONS Percent Percent work Ankle elongation, percent work Kneeelongation, percent Example of re- 01' renumber covery 3 covery 3 5 1015 20 25 0 Bifil ialse-tm'st Standard knit 1 50.3 18 27 48 78 113 14558.3 18 22 32 45 58 75 stretch hosiery. 6 64.2 10 16 34 63 100 130 63.2B 12 23 52 70 11 Round filament (also-twist standard 1 43.7 14 20 40 6387 113 54.0 12 17 30 47 05 711 knit stretch hosiery. 6 50.5 2 5 22 43 721 103 50.4 3 7 10 30 55 7d 13 Bicomponent standard knit stretch 1 44.018 25 50 86 137 200 53.2 18 25 45 7'3 105 14'. hosiery. 6 48.2 4 12 a207 121 105 50.1 7 12 :10 05 05 1:15 7A Triangular cross sectiontalsetwist. 6 52.0 1 5 25 50 80 105 47.1 1 3 12 22 10 50 8 Bitilamcntcross section standard 1 44.4 300 400 800 1.200 1.700 2, 300 45. 0 300500 550 1 320 2.000 1.000 knit hosiery Nylon 6. 6 50.0 50 00 300 7001.300 2,100 00.4 t 350 500 1,500 1.000 6 Round cross section Standardknit 1 30.0 400 050 1,300 2,000 2.800 3.000 41.0 300 500 050 1,350 1,5001.300 hosiery Nylon 5. 5 50.0 0) 50 400 1,100 2,100 3,300 52.5 450 1 :101.400 2.100 14 Bifilament cross section Mesh'knit" 1 40.6 45 800 2,0003,400 5.000 6,500 45.7 200 3'10 050 1,100 1.700 -Nylon 5. 6 57.5 ("1 5001,800 3, 700 0.200 01.2 300 500 1,300 7 Triangular cross section Mesh- 138.7 500 1,000 2,200 3, 520 4,900 0 250 41.1 200 32 700 1,200 1,800knit++-Nylon 0, 0. s 58.5 (0 o 400 1,700 3,000 5,800 58.8 200 500 1,350

Standard knit, plain or jersey stitch. +The values in the table are allexpressed in grams with the exception Too small to read on Instron on10,000 gram load scale. of work of recovery. 'Load too small to show onchart. Mesh kn1t=tuck stitch.

Work of recovery is the ratio of recoverable w rk t round cross sectionhas an, immeasurably small value. the total work required to strain afiber or fabric a spec-, 20 Blfilament y Containing Percent z and 2 ifid unt und r a iv program f strain rate, I percent Ti0 were converted tofalse-twist yarns similar hi case, i was d i d at 25 percent elongation15 to that described for Example 9 and exhibited similar sec nd f ard ccl 15 s d return d was l. 7 elastic properties in test hosiery as thatillustrated in culated a cording to ASTM D 1774-64, ASTM St Table 2 forExample 9. Likewise, bifilament cross secdards (1964) part 25, pp.428-432. 25 tion yarns containing 0.3 and 2.0 percent of T10 were Allval e for Table 2, 3, 4 and 5 were measured converted tostandard jerseyknit hosiery. The bifilausing lnstron G61-3C 2-inch r bb r faced ant dment yarns containing T10 exhibited similar elastic jaws clamped with 60pound pressure. The cross head properties as that of Example 3. Thebifilament falseand gage length were the same and a 25 percent elontwistyarn of Example 9 might be additionally comgation was achieved in 15seconds. There was 2 in h 30 pared with the triangular cross sectionfalse-twist Yarn of hosiery between the clam ed jaws and lengthwi ofExample 7A in the form of similar hosiery. As can tests and 1 inch ofhosiery between clamped jaws in the be Observed, the Work of reco ry fort riangular transverse or width tests. cross section false-twist yarn issignificantly less than The bicomponent and triangular yarns evaluatedbifil false-twist yarns and the elongation after six cycles herein aresold commercially. at 3 percent elongation was 1 gram compared with 10The elastic properties of the hosiery on lengthwise grams, or about 10Percent Of that Obtained for the extension are given in Table 2. As canbe seen the ankle bifilament yarns at the ankle section of the hosiery.and the knee areas were selected since these are the Likewise, thetriangular cross section yarn hosiery in areas of greatest wrinkleproblems in ladies hosiery. the knee section had significantly less workof recovery Referring to the results shown in Table 2, it can. be andvery low load to O loads at 3 percent elongation noted that thebifilament false-twist yarns have the than did the bifilament crosssection of Example 9 highest work of recovery of all yarns tested andthe im which had a stress force of 9 grams when tested in the provementin terms of work of recovery is the greatest knee section. Thus, itshould be expected that the trianafter 6 cycles when compared to othertypes of yarns gular cross section yarns generally would have greatertested as indicated by Example 9. Most significant in problems Withsagging and wrinkling than would the the stress-strain curve was thestress force at an elongabifilament yarns of this invention. tion of 3percent. It can be noted that the hosiery of Ex- Examples 14 and 7,respectively, show a comparison ample 9 had a stress force of 16 gramswhich was 250 of bifilament cross section with triangular cross sectionto 500 percent higher loading in the ankle area at 3 perin a mesh knitstocking. Generally, the elastic propercent elongation than the roundcross section falseties are approximately equivalent to the triangulartwisted yarn (Example 1 l) or bicomponent stretch hocross section in themesh knit hosiery. It is believed that siery (Example 13). Without falsetwist, the bifilament failure to show equivalent advantages here may bedue cross section, plain knit or jersey knit hosiery (Example to tuckknit stitch on long courses having reduced twist 3) may be compared withthe round cross section am and, consequently, this type stitchinterferes with the (Example 6). The work of recovery on the first c lability of this yarn to twist at stitch doubling areas. is 44.4 percentor 10 percent higher for the bifilament The data for Examples 9, and 13are shown cross section than the round which would indicate defig philly in FIGS 16 and respectively, and nitely improved wrinkle resistance.in Table 2, it can be th pi u e of th knit h st? of Example 9 is shownin observed further that the bifilament cross section yam EXamPle 1 1 inand pl 13 in (Example 3) has greater elasticity after 6 cycles ofextenslon thefound cross sfictlon of P knit and The bifil cross sectionmesh knit hosiery has 5 to 10 less force requlred to extend It to 25 P hIndeed, percent greater work of recovery in the knee section the Stressforces are about one'half that requlried to than does triangular crosssection mesh knit yarn, both tend round cross sect1on yarn of an equaldenier. After b i d employing a k k i i h Aft i six cycles of extensionthe bifilament cross section plain knit hosiery has a stress force of 50grams which indicates excellent capacity to retain its shape, whereasthe cles, the bifil cross section appears to retain 50 percent moreforce in the knee section at 10 percent elonga tions. However, in Table3, it can be observed that in the transverse direction, the bifilamentmesh knit hosiery after six cycles, has a stress force of grams at 3percent elongation and at the knee section and at the welt section.Additionally, after six cycles, the power of recovery (see Table 4 ofthe bifil mesh knit in the lengthwise knee area was 150 grams or 150percent greater than that for the triangular cross section.

In Table 3, bifilarnent false-twist yarns (Example 9) are superior toround false-twist yarns (Example 11) and bicomponent round cross section(Example 13) in plain knlt in a transverse direction over the entirerange of elongation and at 25 percent elongation, especially after 6cycles of extension. The values vary between 200 percent and 100 percenthigher for Example 9 than for Examples 1 1 and 13 in the transversedirection. For bifilament plain knit hosiery (Example 3) as comparedwith round plain knit standard hosiery (Example 6) it can be observedthat the transverse force elongation Values are much higher and wouldrepresent a more comfortable extension force than that obtalned forround cross section. After six cycles, the values for the bifilamentwere adequate to avoid wrinkling and obtained a smooth fit in the anklereglon and in the knee region.

Example 7A, triangular cross section false-twist yarns had similarproperties in transverse direction to that of the bicomponent yarns upto a 10 percent elongation; however, at 10 percent elongation and above,very rapid loading ensued which indicated a lower degree of elasticityfor the triangular cross sections of this yarn.

Table '4 illustrates a more significant part of the elastic properties.In this case the yarn was extended to 25 percent elongation and allowedto return to 12- /& percent elongation and the force in gramsascertained at this point by reading from the chart. This value isdesignated as the power of recovery, and is frequently referred to asthe muscle power of the fabric and is probably a more significant valuethan is the forward extension part of the cycle. As can be observed inTable 4, bifilament false-twist stretch hosiery (Example 9) after sixcycles of lengthwise stretch has a power of recovery of 25 grams or 300percent greater force at the ankle as compared with the bicomponentround cross section false-twist stretch yarn. Additionally, thebifilament yarn has significantly higher values in the knee section.

In Example 9, bifilament false-twist stretch hosiery after six cycles oflengthwise stretch has at least 200 percent greater force at the ankleas compared with a triangular cross section (Example 7A) falsetwiststretch hosiery of identical construction.

A similar improvement for Example 9 over Example 1 l and Example 13 canbe observed for the power of recovery in the transverse direction. Thepower of recovery for bifilament yarn (Example 3) in the knee section is125 grams or approximately twice that of the roundcross section (Example6) in the lengthwise direction. The power of the recovery of 175 gramsfor bifilament cross section mesh knit yarn (Example 14) isapproximately twice that for the triangular cross section mesh knithosiery (Example 7) after 6 cycles of extension.

TABLE 3.HOSIERY PHYSICAL PROPERTIESTRANSVERSE Ankle elongation,Below-welt-thigh area percent elongation, percent Example Number N o. ofcycles 3 5 10 25 9 Bifil F.T.... 6 5 7 12 Round RT. 6 1 3 5 26Bicomponent 6 3 6 15 Triangular cross 6 2 5 3 Bifil plain 6 5 1O 50 190Round cross section 6 4 10 100 470 Bifil mesh knit 6 5 10 40 380Triangular mesh knlt 6 5 10 35 185 Plain or jersey knit.

NOTE-RT. False twist.

TABLE 4.POWER OF RECOVERYEXTENSION TO 25% ELONGATION WITH MEASUREMENT OFLOAD ON RETURN TO 136% ELONGATION Transverse or width Lengthwise ofhosiery direction of hosiery Number of luxnninlu number cycles AnkleKnee Thigh Ankle Knee Thigh u 1min ltllSl! twist" fg l l4 l2 7 6 8 8 5 35 3 3 1 l2 l8 6 7 12 3 5 5 5 6 12 7 1 250 150 3 hwiery" 6 125 100 20 4o50 6 Round hosiery" 8 2g "5 ".3 14 m a 252 "is 7 Triangular mesh knitsparkle yarn 5 '12 Force in grams after extension to 25% elongation andreturn to 12%% "Plain or jersey knit.

'"No data.

TABLE 5.MAXIMUM ELONGATION OF HOSIERY- STRETCH AT ANKLE Percentelongation-after one ycle Where 500- L000 yield 2,000 Example gram grampoint gram number load load occurs load 9 Bifillfelse-twist 85 101 84120 stretch hosiery. 11 Round false-twist 84 98 80 118 stretch hosiery.13 Bicomponent round 36 56 36 80 stretch hosiery.

From Tables 2 through 5 the following general conclusions may be drawn:

1. Bifilament false-twist yarns (Example 9) on repetitive cycling havesubstantially improved elastic properties as compared with Examples 1 1,7A and 13 over the entire range of tests evaluated.

2. Bifilament cross section yarn in standard knit hosiery (Example 3),as compared with round cross section in standard knit hosiery, has someslightly improved properties after one cycle and significantly improvedproperties after six cycles over the entire range evaluated.

3. Bifilament cross section mesh knit hosiery (Example 14) has equalproperties over most testscmployed and slightly to significantlyimproved properties after six cycles of testing as compared with atriangular cross section mesh knit hosiery.

it is observed that the bifilament yarns (Examples 2, 3, 8, 9 and 10) ina ZO-denier exhibited approximately the same sheerness of that observedfor a l0-denier monofilament. This is because bifilament yarns wherethey cross at the stitch point present the narrow edge of the bifilamentto view. Thus, at the point of maximum abrasion or compression onepresents the best geometric area for breaking resistance while theminimum geometric area is presented to the eye, thereby achievingsheerness and simultaneously good wearing qualities of the hosiery.

Panel jury tests of 20 women in wear tests of a single size hosiery madeof false-twist bifilament yarns (Example 9) rated them as sag-freehaving excellent wearing qualities and having exceptional aestheticqualities in appearance. They rated the comfort fit over an entire rangeof leg sizes of 8- /6 to 10-% as excellent. The wearing qualities werequite superior to other hosiery such as Example 1 1, false-twist roundcross section hosiery, Example 7A triangular cross section false-twisthosiery, and Example 13 bicomponent standard knit stretch hosiery. Thebicomponent hosiery in all examples were composed of nylon 6,6 as thesheath portion which is about 35 percent by weight and nylon 6,l06,6copolymer in the core portion generally in the kidney shape as 65percent of the total.

The above hosiery fashioned from bicomponent and triangularcross-section yarns were purchased for comparative evaluations.

EXAMPLE l5 Bicomponent yarn was prepared by the procedures described inExamples 1-14 except nylon 6,6 was employed. The bifilament yarn wasfalse-twisted and compared with similar hosiery made from false-twistround cross section yarn. These were tested for work of recovery, andstress-strain curves similar to those indicated in Tables 2, 3, 4, and5. The bifilament hosiery made from polyhexamethylene adipamide showedapproximately equivalent improvement in all physical properties and inluster effects as that already described for polycaproamide whencompared with the round cross section made under identical conditionsexcept with respect to the spinnerettes employed. The spinningtemperature was maintained at about 280C to produce a glace look fromthe polyhexamethylene adipamide (nylon 6,6).

EXAMPLE l6 Poly[bis(para-aminocyclohexyl)methane dodecamides] was spunat a temperature of 290C through bifilament spinnerettes of the typeillustrated in FIG. 1 and was drawn at a draw ratio of 3. The drawn yarnhad a density of 1.001; a moisture absorption of 3 percent at 65 percentrelative humidity and a glass transition temperature of greater than C.This yarn was also prepared in round cross section. The same improvementin elastic propertiesfor bifilament cross section in hosiery aftertwisting over the control in round cross section was noted; however, theelastic properties as compared with polycaproamide and polyhexamethyleneadipamide was approximately twice as great in the force in grams at lowelongations of 3 and 5 percent. The work of recovery was between 10 and15 percent higher than that indicated for polycaproamide. The musclevalue or power of recovery was approximately 100 percent greater thanthe polycaproamide listed as Example 9, Table 4, for the ankle, knee andthigh dimensions.

These values are desirable for support hosiery but too high forconventional stretch hosiery, for a comfortable fit.

EXAMPLE 17 A series of runs were made employing polyamides of relativeformic acid viscosity of 25 to 90 using a spinnerette of the typeillustrated in FIG. 1. A range of temperatures from 250 to 290C wereevaluated. The distance between the spinnerette orifices tested was from0.9 to 4.0 mils. Heated quench air immediately below the spinnerette wasevaluated in the range of 260 to 350C and the velocity of the quench airin the vicinity of one-fourth to one-half inch from the spinnerette facewas evaluated in the range of 0 to 8 standard cubic feet/minute/25pounds per hour throughput. Polymer throughput was evaluated at a highrate, 8 grams/- minute/bifilament and at a low rate of 2 grams/minute/-bifilament. The spinnerette orifice length of 20 to mils was evaluated.

entation of reflection which in turn increases the glace look.

TABLE 6.PROCESS FOR CONTROL OF MODIFICATION RATIO Approx. rel.

effect on Assuming mod. ratio, value on left Signifipercent as increasesGlace-look "Scintilla look" cance corn ared effect on level with 0. 1mod. ratio Range Preferred Range Preferred Polyamide relative formicacid viscosity 1 Increases 2565..... Mils between spinnerette orifices 2Temperature, C 3 Heated quench, C. medium imme ately 4 belowsplnnerette. Quench air rates in the vicinity of the spin- 5 25Increases 0.1-1.0 s.c.f.m 0.1-0.5 s.c.f.n1. 4-8 s.c.f.m. 6-8 s.c.f.m.

nerette. Polymer throughput 6 20 Decreases. High 4.68 g.p.m Low Low.Spinnerette orifice capillary:

Length efiects 7 10-15 Increases Short Short Long Long. Length in mils8-80.. 8-l50. 8-150... -150. Length/diameter C") 0.8-3.0. 0.8-2.0. 2-202-10.

4-8 grams per minute per bifil filament. "2-6 grams per minute per bifilfilament orifice.

Since tricot knits have a stitch very similar to the plain knit, e.g.,jersey knit stitch, fabric made by tricot knitting exhibits similarelasticity utilizing the bifilament yarn of this invention. Generally,it can be said that tricot fabrics have about 50 to 60 percent lesselasticity than jersey knit products. By utilizing bifilamentfalse-twisted yarns one can achieve approximately equivalent elasticityin the tricot knit wear as that ob tained for jersey knits of roundcross section which greatly enchances the elasticity of tricot knits.These bifilament yarns find utility in womens slacks, in swim wear,where the characteristics'of high sheen, high gloss combined with theelastic properties considerably enchances the utility of the textilearticle made from bifilament yarns.

Additionally, particularly where sheer fabrics and styling aredesirable, such as in intimate wear, e.g., nightgowns, housecoats,lounge suits, negligees, peignoirs, and the like, these bifilamenttextile articles have high utility. Tricot knit fabrics and other flatfabrics may be further modified in appearance by employing processesknown as wet-calendering and frictioning calendering. Generally pastelcolor favors the glacelook. The so-called ice or basic dyes insure thatthe glace-look" is maintained in the finished dyed article. In mixedfabrics, dark dyes decrease the glace look and bright dyes increase theglace look. Polyamides having an amine end group of or less may be dyedat a pH of 7 with basic dyes and an amine group of 40 to 50 using a pHof 8 with basic dyes. Using an amine end group as high as 70 to 75millequivalents per kilogram of polymer, polyamides may be dyed at a pHof 8.5 with basic colors. Other means of increasing the glace look areplaiting of glace look yarn on the front of a darkcolored backing yarn.If the low modification ratio bifilament yarns of this invention areemployed in jersey knit articles and only in the wales essentially thesame glace look is obtained as if the bifilament yarn were includedthroughout the textile article. However, this is at a considerable lossin the elastic properties of the textile article. A considerableincrease in the glace look can be obtained by doubling the number ofyarn ends in the wales. An opposite effect is obtained if one doublesthe number of yarn ends in the courses, since this tends to emphasizesparkles.

By alternating wales using bifil yarns, the pattern responds to verticallight which tends to highlight the ori- '"Capillary length isproportional to diameter; thus a larger diameter requires a longerlength. A better characterization of this is the spinncrette capillarylength divided by the splnnerette capillary diameter.

It has been found that the high luster and high sheen characteristics ofthe bifilament yarns of this invention, whether false-twisted or othertexturing systems are employed, the reflectivity is relatively unchangedafter washing from the original textile article prior to soiling.Therefore, the apparent soiling of such fabrics is largely overcome by aminor reduction in the sheen and the general appearance with respect tosoiling is considerably superior to other cross sections such as round,triangular and the like although treated in the similar manner. Thisproperty is of particular value in white intimate wear and in pastelcolors which would otherwise show considerable soiling in cross sectionsemployed heretofore in the prior art.

While the production of the bifilament yarn product of the presentinvention has been illustrated utilizing separate orifices, thoseskilled in the art will recognize that other types of orifices may beemployed. For example, two holes connected by a thin slot may be usedthrough proper control of spinning conditions which achieve a bifilamentas described herein.

We claim:

1. A polyamide bifilament yarn comprised of two lobes interconnected bysymmetrically opposed concave sides which form an oblong yarn crosssection characterized by an intercept angle 0 ranging from 41 to 54degrees.

2. The yarn of claim 1 further characterized by a modification ratio ofbetween 1.65 and 2.05.

3. The yarn of claim 1 in which the lobes have substantially circularportions of equal diameter connected by the concave sides, saidcircularity being greater than 0.9.

4. The yarn of claim 3'in which the polyamide is selected from the groupconsisting of polycaproamide, polyhexamethylene adipamide andpoly[bis(paminocyclohexyl)methane dodecamide].

5. The yarn of claim 3 in which the denier is from 1 to 100.

6. A jersey-knit fabric prepared from the yarn of claim 3 in which thefabric has a luster value between 8 and 15 (K/S X units.

7. The jersey-knit fabric of claim 6 in which the yarn has at least 30turns per inch false twist and the fabric has a luster value between 14and 21 (K/S X 100) units.

2. The yarn of claim 1 further characterized by a modification ratio ofbetween 1.65 and 2.05.
 3. The yarn of claim 1 in which the lobes havesubstantially circular portions of equal diameter connected by theconcave sides, said circularity being greater than 0.9.
 4. The yarn ofclaim 3 in which the polyamide is selected from the group consisting ofpolycaproamide, polyhexamethylene adipamide andpoly(bis(p-aminocyclohexyl)methane dodecamide).
 5. The yarn of claim 3in which the denier is from 1 to
 100. 6. A jersey-knit fabric preparedfrom the yarn of claim 3 in which the fabric has a luster value between8 and 15 (K/S X 100) units.
 7. The jersey-knit fabric of claim 6 inwhich the yarn has at least 30 turns per inch false twist and the fabrichas a luster value between 14 and 21 (K/S X 100) units.